From owner-freebsd-current@FreeBSD.ORG Wed Jul 21 08:23:40 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 96CDB16A4CE; Wed, 21 Jul 2004 08:23:40 +0000 (GMT) Received: from thekla.de.clara.net (thekla.de.clara.net [212.82.225.81]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9A5E143D2D; Wed, 21 Jul 2004 08:23:37 +0000 (GMT) (envelope-from michael.riexinger@de.clara.net) Received: from localhost.de.clara.net ([127.0.0.1] helo=localhost) by thekla.de.clara.net with esmtp (Exim 4.30; FreeBSD) id 1BnCNo-000INN-9E; Wed, 21 Jul 2004 10:23:24 +0200 Received: from box.int.de.clara.net ([192.168.0.226]) by thekla.de.clara.net with esmtp (Exim 4.30; FreeBSD) id 1BnCNZ-000IH9-Jx; Wed, 21 Jul 2004 10:23:09 +0200 Received: from box.int.de.clara.net (localhost [127.0.0.1]) i6L8NqwU002784; Wed, 21 Jul 2004 10:23:52 +0200 (CEST) (envelope-from michael.riexinger@de.clara.net) Received: (from mriexi@localhost) by box.int.de.clara.net (8.12.11/8.12.10/Submit) id i6L8NqZv002783; Wed, 21 Jul 2004 10:23:52 +0200 (CEST) (envelope-from michael.riexinger@de.clara.net) X-Authentication-Warning: box.int.de.clara.net: mriexi set sender to michael.riexinger@de.clara.net using -f Date: Wed, 21 Jul 2004 10:23:52 +0200 From: Michael Riexinger To: Dan Nelson Message-ID: <20040721082352.GA2005@box.int.de.clara.net> References: <056801c46eb3$bd0e2a40$45fea8c0@turbofresse> <20040721044816.GA56020@dan.emsphone.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040721044816.GA56020@dan.emsphone.com> User-Agent: Mutt/1.5.6i cc: jesk cc: freebsd-current@freebsd.org cc: Robert Watson Subject: Re: I/O or Threading Suffer X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Jul 2004 08:23:40 -0000 On Tue Jul 20 23:48:17 2004, Dan Nelson wrote: > In the last episode (Jul 21), jesk said: > > i figured out that the performanceloss only really occur if the > > process is heavily writing on the filesystem. dd if=/dev/zero > > of=/dev/null bs=128k doesnt hurt much in responsetime of parallel > > processes, but when dd operates on the filesystem with of=foo every > > process will be affect in executiontime. a simple ps or ls meanwhile > > dding onto the disk will be hang for dozen of seconds. > > Ah. now that's a different story. You're out of the control of the > process scheduler and into the disk. I don't suppose you're using an > IDE/ATA disk with no tagged queueing? :) Run "dmesg | grep depth.queue" > to see how many requests can be queued up on your disk at once. > > That dd is stuffing lots of dirty data into the disk cache, and all the > other processes have to wait in line to get their I/Os done. You'll > see much better results from a SCSI disk (with usual queue depths > between 32 and 64), and even better results from a multi-disk hardware > RAID array (which will have a large write cache). Same here. I tried both with IDE and SCSI. With IDE it's terrible, ps for example takes seconds to execute. With an 2 cpu machine with scsi hdd's, it's better but there's some delay, too. I tested on a FreeBSD 4.9 machine with ide disks and there is no delay, it works perfect. That makes FreeBSD-5 really unusable for me. Best regards, Michael Riexinger systems engineer -- claranet gmbh internet service provider tel +49 (0) 69 - 40 80 18 - 300 email: michael.riexinger@de.clara.net http://www.claranet.de/